1. Field of the Invention
The present invention relates to a wrap film suitable mainly for wrapping food and to a wrap product comprising the wrap film and a dispenser box having the wrap film placed therein. In particular, the present invention relates to a wrap film using aliphatic polyester resin, wherein the wrap film is easy to use in view of its improved clinging property and pulling-out property.
2. Related Art
Heretofore, a thin film made of thermoplastic resin has been used for food that must be stored or heated with a microwave in food-related businesses such as restaurants and food stores or at home. Among them, a wrap film of vinylidene chloride copolymer resin has multiple excellent properties such as resistance to damping, oxygen gas barrier property, heat resistance, clinging property to containers and transparency making it a popular item for use as a film for wrapping food. In addition, a wrap film made of polyethylene or polypropylene, which is a non-chloride resin, has been developed and marketed these days.
These wrap films demonstrate the necessary properties as a wrap film such as clinging property and gas barrier property by taking advantage of features of composed resins and composition of additives. Among these necessary properties, clinging property and pulling-out property from the state where a wrap film is wound around a paper core are the important properties which greatly influence its ease of use.
On the other hand, a wrap film made of aliphatic polyester such as polylactic acid resin, which is considered to be more harmless and has less of an environmental impact, has been proposed (for example, in JP-A-2000-26623, JP-A-2000-26624, JP-A-2000-26625, JP-A-2000-26626, JP-A-2000-37837, JP-A-2001-96701, JP-A-2001-106805, JP-A-2001-106806, JP-A-2000-185381, JP-A-2000-302956). All of these documents provide a wrap film having an excellent clinging property by using an aliphatic polyester resin such as polylactic acid resin. However, these documents do not teach how to control the pulling-out property so that the resultant film rolls are poor in balance of pulling-out property and clinging property and insufficient in ease of use.
Further, a flexible aliphatic polyester resin film that is not a wrap film is disclosed in JP-B-3105020, JP-B-3178692, JP-A-11-222528, JP-A-2001-49098, JP-A-2002-60605 and the like. However, none of the films proposed in these documents are intentionally given a clinging property and is therefore deficient in this property. In addition, none of them discloses information regarding the pulling-out property, and none seeks to improve the ease in use by considering both properties. JP-A-2002-60604 and JP-A-2002-60606 disclose films obtained by a non-stretching or an uniaxial stretching method. However, these films have insufficient ease of use owing to poor size stability when exposed to a high temperature such as heating in a microwave and poor cutting property, i.e., the film stretches and is cut in different directions from that which was intended when being cut with the blade of a dispenser box. Moreover, since the pulling-out property is not specifically considered and special means from the viewpoint of control of clinging property is not provided, the films sometimes deteriorate in the balance between clinging property and pulling-out property.
Furthermore, the technology for controlling surface roughness of a polylactic acid resin film is disclosed in JP-A-2001-592029. However, this document teaches that the surface roughness can be controlled by mixing inorganic particles having an average particle size of 0.1 to 5 μm so that the surface roughness is on a level of μm, which is greatly different from the range of surface roughness aimed in the present invention. In addition, the film obtained therein is not intended to have an improved clinging property so that the clinging property is insufficient.
As described above, there has been room left for further improvement in order to obtain an easy-to-use wrap film by using a resin considered biodegradable such as aliphatic polyester resin.